Metal pickling



Luz. COMPOSITIONS,

l w H re atta Jiihe 21, 1927.

UNITED STATES JAMES H. GRANELL, OF ELKINS PARK, PENNSYLVANIA.

PATENT OFFICE.

METAL PIGKLINGI Il'o Drawing.

This invention relates, generally, to pickling metal, particularly ironand steel, 1I 1 a pickle bath, and it consists in the provision of aregulator for causing the acid of the pickling bath to selectivelyattack unclean portions of metallic surfaces to the exclusion orsubstantial exclusion of the clean portions of the metal surfaces.

The principal objects of the invention are to prevent the pickle fromattacking clean metal, or more accurately, clean portions of the surfaceof the metal; to avoid the escape of poisonous vapors from the picklevat to obviate over-pickling and pitting the work; to economize in theconsumption of acid; to avoid rusting of the pickled work; to reduce thelabor of making up pickling baths; to minimize the amount of metal lostin pickling; to cause the pickle to concentrate its energy on the scaleremoval only; to remove rust and scale from threaded, machined, andpolished stock even if of high carbon steel without marring the finishor altering the dimensions; to provide for the use of a wider range ofpickling temperatures; to increase the efficiency of the picklinoperation and to prolong the life of the pickling bath; to produce cleanwork; to speed up the pickling operation; and to keep the atmosphere ofthe pickling department free from rust forming or promoting elements.

In the art of pickling the metal is treated with dilute acids to removerust and scale,

after which the metal is washed with water and dipped into an alkalinebath to remove the last traces of free acid. The acid removes the rustand scale but unfortunately from the pickling standpoint it attacks thecleaned metal itself, producing an evolution of hydrogen gas whichescapes into the air, carrying with it a fine spray of the pickling bathproducing an atmosphere of great rusting properties and one which ishighly injurious to health. The attack of the pickle on the metal itselfnot only wastes valuable metal but also uses up the strength of the 1acid which should be directed to removing the rust and scale.

By the present invention these objectionable features of the picklingprocess are overcome to such an extent that from a commercial standpointthey can be considered eliminated. To accomplish this in accordance withmy invention I add to the pickling bath a regulating agent oringredientwhich Application filed April 15, 1926. Serial No. 102,311.

especially effective in connection with sulphuric acid, which is theacid generally used for pickling iron and steel.

In order to produce the pickle regulator of my invention, I animal or.vegetable materials n bearing proteid, such .as. albumi -noids, andcondense the distillate to secure a liquid containing or constituting apickle regulator which in association' with a pickle bath profoundlyalters the action thereof on the work, making the action selective withrespect to the surface condition of the metal. The proteid bearingmaterial may, among other things, be hair, gri stle, hides, skins,fiesh, casein, ossein, elatine, etc. As a practical example gelatine maybe used. This is placed in a still in the regular way. The still is thenslowly heated until nothing remains but charred coke, and products ofthe destructive distillation are collected in a reservoir or condenserin liquid form. A little animal or vegetable fat added to the gelatinebefore distillation assists in the operation by better distributing theheat throughout the mass and increasing the yield of control material.

The substance or material which I have termed distillate may be used intoto but I prefer to use. the water insoluble portion only, because ofits superior control" action. This insoluble portion apparently consistsof a series of basic materials so proportioned as to exert a powerfulcontrol efiecta To produce a pickling bath according to my invention, Imay use the following formula:

Water 1000.00 gallons, sulphuric acid (66 B.) 50.00 gallons, waterinsoluble portion of distillate .125 gallon.

The ingredients may be mixed in the order given or thendistillateamaymbemixed with a small portion of the acid (one part ofthedistillateandthree' parts of the acid) tiiaaadedaaer the bath has been made'up.Thedistillate may be varied to increase or diminish its control action,and it is'evident to those skilled in the art that the amount and kindof acid may be varied to produce a strong or weak bath. An equivalentamount gallon, hydrochloric acid (1.20 sp. gr.) 1

of nitre cake or similar acid bearing material can be used to replacethe free acid if desired.

Ihg water insoluble distillate dissolyes-in the acid batlihi'ithturbidity use selectively Eliecks the"attack*of"the acidonclean'm'etal,

eliminating to a large extent the generation of hydrogen. What littlehydrogen is produced is caught in a blanket of foam produced by theeffect of the distillate and held in the foam long enough to deposit allcondensed moisture before it escapes to the air, thereby removing allpossibility of an obnoxious atmosphere such as would cause rust andinjure the health. The pickling bath may be used at any desirabletemperature from ordinary room temperatures up to boiling, as suchtemperatures have no decomposing effect on the distillate, but as theactivity of the acid increases with the temperature of the bath, moredistillate should be used as the temperature is increased. The amount ofdistillate given in the formula is suitable for pickling baths run atapproximately 17 5- F. Generally stated, the amount of distillaterequired is that which will prevent the visible generation of hydrogen,known commercially as gassing. owever, I have found in certain caseswhere a large amount of distillate is required that an excessive andobjectionable foam is produced which clings to the work and ma'rs itsappearance, especially where the bath is highly heated.

This defect I have been able to correct by the discovery that thedistillate consists of two component parts, one soluble in commercialhydrochloric acid and one that is not, and that the portion soluble inhydrochloric acid causes the pickle bath to act selectively and that theother portion produces the foam. I may therefore separate the extractinto these component parts and use the acid soluble portion as my pickleregulator, which Iterm extract. To make the extract I m use thefollowing formula:

Water insolu le portion of distillate 1 gallons.

The ingredients are thoroughly mixed which causes the generation ofconsiderable heat, and then allowed to separate into two layers ofliquid, the bottom layer being the extract, which I separate from thetop layer by drawing off. Concentrated sulphuric acid cannot be used forthis separation as it dissolves the entire distillate but equal volumesof sulphuric acid and water, forming a strong acid solution, may be usedwith satisfaction although I have found the yield is not quite equal tothat of hydrochloric acid. My observations indicate that the presence ofhydrochloric acid materially increases the control action of bothdistillate and extract.

Commercially I may use'the extract according to the following formulafor pickling iron and steel:

Water 1000.00 gallons, sulphuric acid (66 B.) 50.00 gallons, extract .50gallon.

This formula also produces a foam when acting on the metal but the foamis not as objectionable in character as produced by the distillate.

The described pickle control or regulator in the pickle bath restrainsthe action of the acid on free clean metal and therefore greatlydiminishes the generation of hydrogen gas which action, in connectionwith the blanket of foam produced, entirely eliminates .the escape ofall injurious and rust producing fumes. As my pickle regulator causespra'ctically all attack of the acid to stop as soon as the scale orcoating is removed, pitting and over-pickling are reduced as evidencedby the ability of my pickle bath to remove rust and scale from threaded,polished and machined parts without marring the finish or altering thedimensions. As the acid is prevented from attacking the metal no wasteof metal or acid occurs as indicated by tests where a saving of 60% ofthe acid and 3% of the metal was noted. As acid is not wasted the samepickle bath will pickle a larger quantity of material, and, therefore,the bath does not have to be made up so often and hence there results asaving in the labor of making u pickling baths. Heretofore care had to eexercised not to have the pickle too hot or too strong in acid, or both,because there was danger of pitting or over-pickling the metal, but bymy invention the temperature and the acid concentration of the bath maybe eatly increased in order to diminish the t1me required for pickling,with less danger of pitting or overpickling.

It has been noted that steel tubes and other articles treated accordingto my pickling process drew with greater ease and resist rusting betterthan if pickled in the old way where only sulphuric acid is used, and ithas also been noted that in drawing tubes pickled according to myinvention, a peculiar odor is noted atthe dies. An investigation ofthese effects disclosed the fact that the acid of the bath causescertaino ti ons of the distillajftojbf'co'mg solubleffin the'fajijueous 5athand that when the work, wet with tffiimsolutiaiiyis 'rieutralized'in theregular way by dipping with lime or other alkaline bath, the dissolveddistillate is precipitated on the work in the water insoluble form andalthough in minute amount, acts to assist lubrication and rustprevention.

To those skilled in the art it will be evident that the composition ofthe distillate constituting the pickle regulator of the presentinvention, is complex, and that the philosophy of its action in causinga pickle bath to act selectively and to remove unclean or 252.COMPOSITIONS,

oxidized metal surfaces and to spare clean or bright metal surfaces issubject to various explanations, but from the foregoing descriptionthose skilled in the art will be able to practice the invention, which,for the reasons stated, is not limited to details of procedure, or tothe precise ingredients mentioned, or to mere matters of form, orotherwise than as the prior art and the appended claims may requireunder and subject to the range of equivalents appropriate in chemicalcases.

I claim:

1. A pickle regulator for selectively controlling the action of metalpickling baths comprising the portion of the distillate from animalbodies which is insoluble in water and is soluble in hydrochloric acidand in equal volumes of Water and sulphuric acid.

2. A pickle regulator for selectively controlling the action of metalpickling baths comprising the portion of the distillate from proteidswhich is insoluble in water and is soluble in hydrochloric acid and inequal volumes of water and sulphuric acid.

3. A pickle regulator for selectively controlling the action of metalpickling baths comprising the portion of the distillate from gelatinewhich is insoluble in Water and is soluble in hydrochloric acid and inequal volumes of water and sulphuric acid.

4. A pickling bath for metals one ingredient of which is the portion ofthe distillate of animal bodies which is insoluble in Water and solublein hydrochloric acid.

5. Means for confining the etching action of a metal to oxidizedportions of metal surfaces which comprise a pickle regulator being anacid soluble water insoluble distillate from animal bodies.

JAMES H. GRAVELL.

